Is it legal to write a post dated check?

The check is valid with the signature, date is irrelevant in most states in the USA.

You can write a post dated check. However, that does not oblige the payee to wait to negotiate it. The bank of deposit can present it to the drawee bank, which can choose to return it for not being negotiable, or let it clear your account.

Because so much of this work is done via electronic images, very few humans actually see your check while it is being processed.

PS: This is in the U.S. I can’t speak for Canada.

Once you’ve signed you check the receiving party can cash it whenever they wish, regardless of the date on the check. It used to be that most would hold off on cashing a post-dated check (if, indeed, they were willing to accept a post-dated check) out of both courtesy and to avoid the potential headache of a bounced check. However those days much check processing is done by scanning the check and transmitting the image electronically. The computer isn’t going to hold on to the check until the calendar date you prefer. So writing a post-dated check isn’t illegal, but it might not be the most sound financial move these days.

As has been said, not illegal but also places no obligation to not cash before the date. However I have heard of cases where a bank or credit union declined to cash a check whose printed date was in the future (I think financial institutions have some right to use their discretion, and they may also make mistakes).

I wrote over 15 post dated checks by accident at work to our subcontractors. The banks cashed them before the date. This is in the US.

Most tellers have been taught to not accept a postdated check. Because this is a human scrutinzing the item, he/she is more likely to turn away a customer with a postdated item. Once that item hits the automated system, it is unlikely to be noticed.

I wrote that it was illegal. I think. What I meant to say is that it is not a defense. The date on the cheque is not legally binding and is irrelevant a few days here or there and it can be cashed regardless and trying to get the bank to not charge the fee is pointless. And trying to get the casher of the cheque to pay for the fee isn’t going to work either. They have no legal obligation to hold the cheque.

Legal, sure. Binding or effective, no. It’s better to explain your circumstances (briefly, and without too many personal details), discuss payment terms (people can be surprisingly reasonable), and write that check when you have the funds to cover it.